1. Field of the Invention
The present disclosure relates to a system and method for updating a file, and more particularly, to a system and method for updating a plurality of the same files consistently.
This work was supported by the IT R&D program of MIC/IITA [2007-S-016-01, A Development of Cost Effective and Large Scale Global Internet Service Solution]
2. Description of the Related Art
Integrated storage systems obtained by connecting a plurality of computers through a network provide an integrated storage space to users, and are used in a variety of technical fields such as web searching and super computing. Some integrated storage systems generate a plurality of the same files and store the same files in different storage units in preparation for unexpected damage to an original file, thereby increasing the possibility of restoring the damaged file and also the performance of a plurality of clients reading the same files.
Since the above-described storage system has a plurality of files having the same image, all of the same files must be equally updated when an operation for updating a certain file is requested.
When a file A is stored in data servers D1, D2 and D3 and if update operations 01, 02 and 03 for the file A occur at the same, each of the data servers D1, D2 and D3 must perform the update operations 01, 02 and 03. However, because the data servers D1, D2 and D3 are different from one another, the data server D1 schedules the update operations 01, 02 and 03 in a 01→03→02 order, the data server D2 in a 03→02→01 order, and the data server D3 in a 02→01→03. As a result, the data servers D1, D2 and D3 can have different results after performing the update operations 01, 02 and 03.
U.S. Pat. No. 7,065,618B1, which was invented by Ghemawat, filed by Google inc. on Jun. 30, 2003 and issued on Jun. 20, 2006, discloses a method of managing update operations for the same files stored in a plurality of different computers. In the U.S. Pat. No. 7,065,618B1, a master server managing meta-data selects one of chunk servers storing a file and issues a lease to the selected chunk server, and thus the selected chunk server serves as a primary chunk server and other chunk servers serve as secondary chunk servers that can update the file only under the control of the primary chunk server.
However, in the U.S. Pat. No. 7,065,618B1, an interval exists between transmissions of update data and an update request messages, which are to be transmitted from a client to the chunk servers. Moreover, additional costs are required to issue the lease to the primary chunk server, manage the lease, and restore the primary chunk server when it malfunctions.
U.S. Pat. No. 6,138,124, which was invented by Beckhardt, filed by IBM on Jun. 9, 1998 and issued on Oct. 24, 2000, discloses a method of changing a document in a distributed computing system when the document is duplicated and stored in a plurality of storage units. In the U.S. Pat. No. 6,138,124, one document is divided into a plurality of fields, and there are a document sequence number representing the document and field sequence numbers indicating the respective fields. When a predetermined region of the document is updated, only a corresponding field in each of all the duplicate documents is updated. Thereafter, the document sequence number and the field sequence number of each document are adjusted.
However, the above-described technique can be applied to only a standardized document capable of being divided into fields, and it is difficult to apply the technique to a binary file and a large-capacity file that cannot be divided into a plurality of fields.